Operator controlled telephone test system



TO OTHER EXC HANGES Tasr DESK R. J. CURTIS ET AL OPERATOR CONTROLLED TELEPHONETEST sys'rsm Filed Jan. 28, 1947 Nov. 22, 1949 TEST R w awn T 3 a e N A w XR m T Mam RT Tw N E C INVENTORS 19/6/6420 J C'uer/s J/mms 44/4452 nr/ Attorney I MAIN BATTERY Patented Nov. 22, 1949 2,488,808 OPERATOR CONTROLLED TELEPHONE TEST SYSTEM Richard J Curtis, Santa Monica, and James Miller, Los Angeles, Calif., assign'ors, by mesne assignments, to Inc., Chlcago,

Automatic Electric Laboratories, 111., a corporation of Delaware Application January 28, 1947, Serial No. 724,802

7 Claims. (01. 119-4752) Our invention relates to telephone test systems and has particular reference to a system which will enable an operator, testing subscribers lines, to clear the line switch and selectors from the subscribers line without requiring a workman to open the circuit under test.

This application is a continuation-in-part of our application for Telephone test system, Serial No. 621,194, filed October 9, 1945, now abandoned. In telephone practice it frequently occurs that trouble develops upon a particular subscribers line, which trouble may be an open circuit condition, a grounded circuit condition, a short circuit between the metallic conductors of the line, or the trouble may be merely that the subscriber has left the receiver off the hook. To locate and clear the trouble, it is common practice for a testing operator, located in one of the telephone oifices, to connect his testing circuits to the subscribers line and by manipulation of current, voltage and resistance measuring apparatusto locate the particular trouble and diagnose its character by a workman sent out from the telephone office.

With the present type of equipment the testing operator can not effectively test a subscribers line until the central exchange equipment has been disconnected from that line since, if the trouble is anything other than an open circuit, the trouble on the line will hold the line switch and selector mechanisms in the central office across the subscribers lines as a bridge.

It is, therefore, an object of our invention to provide a release circuit which may be effectively connected to the subscribers line to release the line switch and selector mechanisms from the testing operators desk without requiring the disconnection of the subscribers line from the central exchange equipment.

Another object is to provide a system in which the testing operator at the test desk may connect the central exchange main battery directly across any subscribers line to thereby apply the same battery potential to opposite ends of the energized selector relay and line relay and thus effectively shunt the coils of such relays.

Another object of our invention is to provide a. system in which the test operator may apply battery and ground connections between the main central exchange battery and the subscribers line with negative battery connected to the negative side of the coils for shunting the line relay and the selector relays connected to a subscribers line under test, while at the same time applying ground to the positive battery side of these coils.v

Another object of our invention is to provide a system of the character set forth, in which a polarity reversing switch is provided in the circuit from the F ST: 951; for reversing the polarity of the battery potential supplied over the testing circuit to automatically reverse the test current supplied to the subscribers line at the end of 'a predetermined interval of time after the testing operator first applies a testing line current, to thereby release theline switch and selector relays in the event the line switch and relays are supplied with reverse current over the normal operating circuits. 7 V Other objects of our invention will be apparent in the following specification, read in connection with the single figure of the drawing whichis a diagrammatic view of a portion of a telephone system incorporating the principles of our invention. p

Referring to the drawings, we have illustrated a typical telephone system including a subscribers station S at which is located the usual telephone equipment including a dial I, a trans= mitter 2, and a receiver tvnormally adapted to remain upon a hook 4. The subscribers station S is connected to acentral telephone exchange office containing the central exchange apparatus, the central exchange being indicated, diagrammatically on the drawing as containing the equipment located Within thedotted outline CE and bearing the legend Central exchange No. l.

The connection of the subscribers station S to the central exchange is made by a pair of telephone conductors 5 and 6 which extend through a main distributing frame designated by the legend MDF. At the central exchange there is associated with thesubscribers circuit a line; switch indicate'd by the rectangle bearing the legend {"line switch and the usual selector equipment indicated in the rectangle bearing the legend selectorff I l The line switch includes aline relay LR; and a line switch of the type illustrated and de-v scribed in Engineering Bulletin 301, Fundamentals of Strowg'er Automatic. Dial Systems, published by Automatic Electric Company of Chicago, Illinois, July 1, 1927, page 20; and in Instruction Bulletin805, published June 1931 by Automatic Electric Company of Chicago, lllin'ois. The line switch includes abridge cut-off switch 1300 and a plunger 1 adapted to be actuated by a pull down coil PDC. The pull-down coil has a pair of windings 8 and 9, and the" construction of the line switch is such that energization of the coil 8 will operate the line switch plunger lever l0 and the bridge cut-off lever II to operate the bridge cut-off switchBCO. V

In the normal operation of the telephone system, the lifting of the receiver '3 from the hook t at the subscribers station will complete a circuit to the line relay LR from a main central exchange battery, indicated by the legend "main battery," through. a conductor l2 to a main battery bus ['3 fromwhich the circuit to the line relay cit- 3 tends by way of conductor I4, the coil I5 of the line relay LR, one of the contacts I6 of the bridge cut-01f switch BCO, thence by conductor I] to 7,

and to ground at 20. The operation of the line w relay LR. will complete a circuit through the coil 8 of the pull-down coil PDC, whichcircuit extends from the battery bus through conductor 2|, the coil 8, conductor 22, contact 23 on line relay LR, and to ground at 24.

The energization of coil 8 of the pull-down coil will cause operation of the line switch plunger 1 to connect the line switch contacts CDE to connect the subscribers station to the first selector of the automatic selector at the central exchange, and operates BCO lever II. The A relay of the selector, when energized, will energize the B relay on the selector, which will, in turn, close its pull-down relay PDC, this circuit extending from the battery bus I3 through conductor 2!, the coil 9, conductors 2B and 21, the contacts 28 operated by the line switch plunger lever Ill, conductors 29 and 30, the contacts D on the line switch, conductor 3|, contacts 25 on relay B, and to ground at 32. The energizing of coil 9 will hold the-line switch lever I depressed and, in addition, will cause the B00 lever I I on the line switch to remain actuated, keeping open the BCO switch contacts I6 and I9.

Under the circumstances described, if trouble develops on the line leading to the subscribers station, the test desk, indicated by the legend "Test desk applied to the dotted outline in the drawing, is rendered unable to test the subscribers line for the reason that conductor of the subscribers line is connected to battery through the upper coil of the A relay in the selectonand at the same time the conductor 6 is connected to ground through the lower coil of the A relay; and any attempt to test the subscribers line 5 and 6 would be defeated because of the battery and ground connections which exist across conductors 5 and 6.

Hence, it is necessary to clear the subscribers line from the equipment in the central exchange. Heretofore the clearing of the line from the central exchange equipment has been accomplished by sending a workman to the main distributor frame to disconnect the subscribers line from the central exchange, whereupon the usual test circuits from the test desk are enabled to test the subscribers line to determine the character of the trouble and its location.

By providing the test desk with a disabling circuit in addition to the testing circuits, the function of which is to shunt the coils of relays connected across the subscribers line, we are able to clear the subscribers line for testing.

To accomplish this result, we connect one of the test conductors 33, which normally extends from the test desk to the central exchange, to the negative terminal 34 of the exchange main battery through resistance lamps 35, and we connect the second test conductor 36 to ground at 49. This is accomplished by connecting conductor 33 through conductor 38, a normally closed contact 39 on a polarity reversing relay 40, conductor 4|, a normally open contact 42 on a control relay 43, and conductor 44 through the lamps 35 to the battery terminal 34, and by connecting the test conductor 36 by way of a conductor 45, normally closed contacts 46 on relay 40, conductor 41, normally open contacts 48 on relay 43, and to ground at 49.

At the test desk we provide a disabling key DA for energizing the coils of the relays 43 and .40 by way of a circuit which extends from the battery bus I3 through conductors 50 and 5I to the coils of the relays 43 and 40, thence from.

' the coils to conductor 52 which extends to a terminal 53 at the test desk, adapted to be con-- nected to a plug 54 by which the test desk may be connected to any one of a number of central exchange stations. From the plug 54 the circuit extends by way of conductor 55 through the key DA to ground at 56.

As will be understood by those skilled in this art, the test desk includes a dialing mechanism 5! by which the testing operator, after plugging the plug 54 in to the set of terminals associated with the main exchange which has reported trouble on one of its subscribers lines, may dial the subscribers number to connect the conductors 33 and 36 to the particular defective line.

. When the connection to the subscribers line has been completed, the testing operator then actuates the disabling key DA, energizing relays 43 and 40.

Relay 43, when energized, closes its contacts I 42 and 48 applying negative battery current from the central exchange main battery to conductor 33 and applying ground to the conductor 36. Thus, the left hand side of the upper coil of selector relay A is connected directly with the negative battery terminal at a time when the right hand side of that same coil is also connected to the negative battery terminal. Also, at the same time, ground through conductor 36 will be applied to the left hand side of the lower coil of selector relay A at a time when the right hand side of that coil is also connected to ground. Thus, both coils of the selector relay A will be shunted. Since both ends of upper coil of the A relay are connected to the negative terminal of the battery, current will cease to flow through that coil. Also since both ends of the lower coil are connected to ground, current will cease to flow through that coil; and relay A is disabled and relay B is de-energized opening its contacts 25 and removing the ground connection from conductor 30. This results in the de-energization of the coil 9 of the pulldown coil PDC and allows the line switch plunger 1 to open its contacts C, D and E, disconnecting the normal circuit to the coils of the selector relay A and removing the ground and battery connections to the conductors 5 and 6, respectively, which had previously existed through the coils of the selector relay A.

The reclosing of the BCO switch contacts I6 and I9 will not result in the energization of the line relay LR, since it will be recalled that the negative battery terminal is now connected to the conductor 5 and the coil I5 of the line relay LR will be eifectively shunted.

Holding the disabling key DA closed, the testing operator now closes his BCO key applying ground to conductor 58, which applies ground to the coil 9 of the pull-down coil PDC, resulting in the operation of the ECG lever I I and the reopening of the BCO switch contacts I6 and I9 effectively preventing the re-energization of the line relay LR and removing the ground 20 from the conductor 6. The conductors 5 and 6 are now cleared from their battery and ground connections in the central exchange, and the test arm desk operator may then use. his measuring. instruments to determine the: character and location-of the. trouble. 1

By providing the test desk. with terminals extending to other exchanges, a single testdesk,

mechanism may be-used to: clear a faulty line in any of the exchanges associated withrthe test desk, the disabling key at the test desk being used to shunt the selector A relay on any line connected toany subscribers; line connected to any of the exchanges. Particular attention is called to the. fact that, by using the central. ex changes own main battery for shunting the coils of the selector A relay, a positive disabling of the A relay is accomplished irrespective of. any resistance variations which may exist between the test desk and a particular subscribers. line, since the. same potential is supplied by the same main battery to both endsv of the coils of the A relay and no adjustment by thetesting operator is required to insure the. disabling of-the Arelay.

The polarity reversing relay 40 is a. slow to operate relay and is interposed the disabling circuit for the purpose of reversing the polarity applied tothe conductors 3-3 and 36 to disable the A. relay coils in the event the normal current flow through these coils is in a reverse direction, the relay 40 reversing the connections to. the. con.- ductors 33 and 36 at a. short time interval after the initial closing of the disabling key DA.

It will, therefore, be observed that we hayemrovided a simple mechanism by which the testing operator may clear a subscribers faulty line from its battery and ground connections in the central exchange equipment, from the test desk and without requiring the manual disconnection of the faulty line. at the main distributing frame.

While we have shown and described the preferred embodiment of our invention, we do not desire to be.- limited; to any of the details of construction shown or described herein, except as defined in the appended claims,

We claim: H i

I. In a telephone system, means whereby a central exchange is connected to a plurality of subscribers lines, a source of current for. said central exchange and magnetically operated switch equipment including magnets and coils for said exchange operated by current from said source in the normal operation of the system and wherein a test system is provided including a test desk, a pair of test conductors and means to .connect said test conductors to any of the subscribers lines; in combination therewith, of means for disconnecting the central switching equipment from a selected subscribers line to which the test conductors are connected, said means including the same source of current at the central exchange which normally operates the system, a switch, circuit contacts controlled by said switch for connecting said source of current across the test conductors, whereby the magnets of the normal switching equipment then connected to the subscribers line will be energized and will have the same potential from said source applied to opposite ends of the coils of said magnets, electromagnetic means for operating said switch, and a circuit controllable from said test desk for actuating said switch operating means.

2. In a telephone system, means whereby a central exchange is connected to a plurality of subscribers lines, a source of current for said central exchange and magnetically operated switch equipment including magnets and coils for said exchange operated by current from said sourceiin the normal; operation of. the. system and wherein a test system is providedincluding a test desk; a pairoi test conductors: and means to connect: saidltest conductorsto any oi the. subscribers lines; in.- combination. therewith, of means for disconnecting the: central: switching equipment irom. a. selected subscribers line to which the test conductors are connected, said means including. the same. source: of currentv atthe central exchange which normally operates the system, a switch, circuit contacts controlled by said switch tor connecting. said: sourceofcurrent across the test conductors, whereby the magnets of: the normal switching equipment then connected to the sulzascribersv line will be energized and. will have the same potential from said source applied; to oppositev ends oi thecoils of said magnets. electromagnetic means for operating said switch, a circuit controllable from said. test desk, for actuating said switch. operating means, and a polarity reversing switch in the: circuit connections between said. source and the test conductors and operablev from said test desk: for reversing the polarity of the potential, applied by said source to the test conductors, 1

3; In a. telephone system, means. whereby a central exchange is connected to a plurality of subscribers" lines, a source of current for said central. exchange and magnetically operated switch equipment including magnets and coils for said exchange operated by current from said source in. the: normal operation oi. the. system: and wherein a test system isprovided. including a test desk, apair of test conductors and means: to connect said, test conductors team; of. the subscrilzversv lines; in combination. therewith,. of means: for disconnecting. the central switching equipment from. a selected subscribers. line to which. the test conductors are connected, said means including the same source of current at the central exchange. which normally operates the system, a. switch, circuit contacts controlled by said switch for connecting said source of current-across the test conductors, whereby the mag nets of the normal switching equipment then connected to the subscribers line will be energized and will have the same potential from said source applied to opposite ends of the coils of said magnets, electromagnetic means for operating said switch, a circuit controllable from said test desk for actuating said switch operating means, a polarity reversing switch in said circuit connections between said source and said test conductors for reversing the polarity of the potential applied by said source to said test conductors, and a slow acting magnet connected to said switch operating circuit to actuate said polarity reversing switch at a predetermined time after a predetermined time during which said circuit is energized.

4. In a telephone system, lines, switching equipment, a power source connected to said switching equipment for operating said switching equipment, means for connecting said switching equipment and said power source to any one of said lines, an automatic test switch having outgoing conductors, control equipment individual to said outgoing conductors, means including a test desk for operating said test switch to extend said conductors to said one line, means at said test desk for operating said control equipment to connect said power source through said conductors to said one line and means responsive to said connection of said power source through said conductors to 7 said one line for'dis'connecting said switching equipment from said one line.

5. In a telephone system, a line, a pair of talking conductors for said line, a first automatic switch for establishing a talking connection from said line, a battery, a positive terminal and a negative terminal for said battery, a line relay for said first automatic switch connected to the said battery, an electromagnetic device connecting said line to said line relay to thereby connect the said pair of talking conductors respectively to the said positive and negative terminals of said battery, a second automatic switch for establishing a testing connection to said line, a pair of testing conductors for said second automatic switch connected respectively to said pair of talking conductors, a control relay individual to said second automatic switch, means including a circuit for operating said control relay, means responsive to the operation of said control relay for connecting the said positive terminal of said battery to the said test conductor which is connected to the said talking conductor which is connected to the said positive terminal of said battery and for connecting the said negative terminal of said battery to the said test conductor which is connected to the said line conductor which is connected to the said negative terminal of said battery to thereby release the connection between said line and said line relay.

6. In a telephone system, a line having a plurality of conductors, switching equipment connected to said line, a power'source' having a first terminal and a second terminal, testing equipment, means for connecting said testing equipment to said line, control devices, means efiective in case said testing equipment is connected to said line for operating said control devices to connect either said first terminal to one conductor of said line andto connect said second terminal to another conductor of said line or connect said second terminal to said one conductor and said first terminal to said other conductor, means responsive to the connection of either said first terminal to said one conductor and said second terminal to said other conductor or the connection of said second terminal to said one conductor and said first terminal to said other conductor, for disconnecting said switching equipment from said line.

7. In a telephone system, a line having a plurality of conductors, a power source having a first terminal and a second terminal, switching equipment associated with said conductors, said first terminal normally connected through said equipment to one of said conductors and said second terminal normally connected through said equipment to another of said conductors, a reversal condition whereby said first terminal is connected to said other conductor and said second terminal is connected to said one conductor, testing equipment, a control key, means for connecting said testing equipment to said line, means operated in response to the operation of said key in case said testing equipment is connected to said line for connecting the same terminals of said power source to said conductors through said testing equipment as is connected thereto through said switching equipment, and reversing means eiiective in case said terminals are connected through the switching equipment in the reverse direction to disassociate said switching equipment from said conductors by reversing the application of said power source to said conductors.

RICHARD J. CURTIS. JAMES MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,371,989 Griffins Mar. 20, 1945 2,389,076 Perry Nov. 13, 1945 

